Raw milk feta may hold anti-Listeria key, say researchers

Feta cheese made from raw milk in Greece may hold secrets that could lead to new methods for battling food poisoning bacteria like Listeria, researchers at the University of Lincoln said.

Panagiotis Chanos told delegates gathered at the Society for General Microbiology's 162nd meeting, that a team at the university had managed to isolate lactic acid bacteria found in untreated sheep milk that could produce antibiotics.

Upon further study, he claimed that samples taken from some farms in Macedonia in northern Greece showed that the friendly bacteria present could therefore potentially be used to kill off food poisoning bacteria.

The findings could result in new ways of preventing food poisoning and other pathogens from entering into dairy and other food products.

Chanos stated that rather than using additives or synthetic preservatives in food, there was a real possibility that processors could now utilise useful bacterias as "micro-allies" in fighting disease-causing Listeria.

Some antibiotic resistant strains of these bacteria have been linked in the past to hospital infections. However, the reseachers said that this did not negate their potential benefits.

"Interestingly, we identified these friendly bacteria as enterococci, more commonly recognised as virulent and/or antibiotic resistant bacteria in hospitals," he added. "We found some strains could produce up to three different natural substances to fight different food pathogens."

According to the researchers, cheese manufactured both within Greece and throughout the Mediterranean region boasts a unique taste due to the presence of the enterococcal bacteria in the product.

Chanos stated that if it were possible to ensure safe use of enterococcal bacteria, there was a possibility they could then be developed to fight food pathogens.

"It is known that enterococci in general may have the same properties as good gut bacteria," he stated. "We hope our bacteria possess these properties too, so they could colonise our small intestine and fight Listeria from within the body."

The researchers singled out Listeria in particular, as they claimed it had been found to survive in conditions that other bacteria had not survived.

Food production, due to the threat of poor heat processing or mishandling particularly in the case of animal products, was highlighted as a major area of concern regarding the bacteria, Chanos said.

He stated therefore that finding further solutions ot combat the problem would be vital in ensuring future food safety.

"We hope that this work will lead to ways of fighting food borne pathogens, using the naturally produced compounds called bacteriocins made by other bacteria," Chanos said. "We discovered that all the useful strains of bacteria that produced bacteriocins were able to grow in extreme conditions resembling those commonly found in foods, including the low temperatures found in our refrigerators and the salty conditions found in some cheese."

Source: 162nd meeting of the Society for General Microbiology (Thursday 3 April 2008)